Pipeline analog-to-digital converters (ADCs) offer very high resolution while converting at very high sample rates. Pipeline ADCs are widely used in base station, ultrasound and test and measurement applications. In most of these applications, it is important to quantify and characterize the noise performance of the ADC. The major noise components of a pipeline ADC are, noise contributed by aperture jitter, reference noise, thermal noise and channel flicker noise. Furthermore, the output of an ADC is also affected by phase noise of the input signal relative to the clock source.
Thermal noise and channel flicker noise are fairly constant over input conditions and relatively easy to estimate. Reference noise depends primarily on the instantaneous value of the input (e.g., number of capacitors in the First Stage getting connected to reference nodes) and can be estimated by giving DC inputs and comparing noise performance for a full scale DC and a zero DC input. Aperture jitter is the most challenging to characterize. It is difficult to isolate the relative phase noise between input and clock sources from aperture jitter. Hence more often than not, characterization of device aperture jitter is biased with source phase noise effects.